JPS6032365B2 - adaptive filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for receiving wideband signals, and more particularly to an adaptive filter for suppressing narrowband interfering signals in such a system.

Modern communications and radar systems increasingly use wideband signal formats for information transmission or transmission functions.

By phase-coding or frequency hopping the transmitted signal, the transmitted energy can be spread over a much wider band than is required over the modulation content of the signal. Since the effectiveness of a communication link is determined by the amount of total energy in the transmitted signal, using a wideband signal where the total energy is spread over a wide frequency band, the amount of energy at a particular frequency can be , thereby making it possible to obtain a communication signal that is largely indistinguishable from background noise. The wideband signal is used in the "Extended Spectrum Location Surveillance System" (Spread), which is assigned to the assignee of the present invention.
-Spectmmpositionomkeonibring
Mr. Grossman, who calls himself
It is also useful for eliminating mutual interference between signals in communication systems such as that disclosed in U.S. Pat. No. 3,714,573 to An.

In radar systems, it is desirable to use carpenter energy for target detection.

By using an extended spectrum transmit signal, the total energy is extended in time and frequency, thereby eliminating the need for high peak power pulses that would cause breakdown in the radar transmitter. When receiving,
The extended spectrum signal is time compressed to form an output pulse equivalent to a radar pulse of higher peak power than that actually used by the transmitter. Perhaps the most common form of extended spectrum signal used in radar systems is the frequency modulated "Chirp" pulse. In this type of system, a signal is transmitted whose frequency varies from the beginning of the pulse to the end of the pulse. During reception, this frequency variation is used in a pulse compression filter to obtain relatively short duration, high energy pulses. Phase modulation is used to obtain extended spectrum signals in both radar and communication systems.

In phase modulated extended spectrum systems, the transmitted signal is rapidly switched in phase to produce a signal with a wide frequency range. On reception, this signal is sampled by a "matching filter" which decodes the transmitted signal and generates short output pulses in response to the correct phase-encoded signal. The matched filter does not provide an output for signals that are not correctly coded or are not coded. In either the proposed system or similar systems that use wideband signals, narrowband signals such as CW or narrowband FM interfere with proper system operation. The narrowband signal, which has a higher signal level than the nozzle-like broadband desired signal, activates the automatic gain control circuit of the receiver with the narrowband signal, thereby suppressing the desired broadband signal. . SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an adaptive filter for suppressing interference due to narrowband signals in a system receiving a desired wideband signal. Yet another object of the invention is to provide a time-delayed reproduction signal (repl.
The purpose of the present invention is to provide a filter such that interference signals are substantially canceled by the ica).

According to the present invention, an adaptive filter is provided that suppresses a narrowband signal in a composite signal containing a desired wideband signal.

The adaptive filter includes signal combining means responsive to the composite signal and the correction signal for combining the composite signal and the correction signal to form an output signal. Means for providing the composite signal to the combining means and means responsive to the composite signal for generating a delayed reproduction of the composite signal are further provided. Finally, means are provided for generating a correction signal in response to both the delayed reproduction signal and the output signal and supplying the correction signal to the combining means to suppress narrowband scattering signals in the output signal. It is being For a better understanding of the invention, and other and further objects thereof, reference is made to the following detailed description taken in conjunction with the accompanying drawings, and the scope of the invention is pointed out in the claims.

FIG. 1 shows a simplified block diagram of an adaptive filter 10 constructed in accordance with the present invention.

For purposes of illustration, the adaptive filter 1 is operated at a convenient intermediate frequency IF and has an input frequency of 50 MHz.
Z and an output frequency of 30 MHZ. The signal supplied to adaptive filter 101 by input 12 is supplied to mixer 18,
The mixer 18 is also provided with a suitable local oscillator signal of 2 MHZ from a local oscillator 20. The output of the mixer 18 is fed to a combiner (adder) 22 and then to a power multiplier 32 and an output signal processing device 33. In the mixer 18, the supplied signal is input to the input IF
It is converted from MHZ of frequency 5 to MHZ of output IF frequency 3. It will be apparent to those skilled in the art that other convenient IF frequencies may be used, and other conventional components not shown here, such as intensifiers and filters, may be included in the circuit. Will. The signal from input 12 is also applied to delay means 16a by switch 14a.

The output of this delay means 16a is a delayed reproduction of the signal provided at input 12. The delay period 7 of the delay means 16a is generally chosen to be the reciprocal of the range of the desired signal being supplied, as will be explained further below. A delayed reproduction signal of the input signal is passed through a limiter 28
a and mixer 26a. A mixer 30a is also provided to sample the outputs of synthesizer 22 and multiplier 32. The output of mixer 30a is a control signal that is fed to mixer 26a by integrating circuit 34a. The combination of the delayed reproduction of the input signal applied to the mixer 26a and the integrated control signal applied to the mixer 26a forms a correction signal, which signal is applied to the switch 3.
6a to the adder 22. Adaptive filter 10 also includes delay means 16b, limiter 28b, integrator 34b, and mixers 26b, 30b,
These are connected by switches 14b and 36b to the output of delay means 16a and to adder 22 in the same manner as above. It should be understood that switches 14a, 14b, 36a, and 36b are not required in the adaptive filter 10, but are included to facilitate explanation of the operation of the adaptive filter 10. be. 1st
Also shown in the figure is a signal processing means 33 that is not part of the adaptive filter 10. This signal processing means 33
should be selected based on the particular type of broadband signal used and is shown in FIG. 1 to facilitate explanation of the operation of adaptive filter 10. Figure 2A
shows the spectral characteristics of the wideband signal used in connection with the present invention. The wide band signal of FIG. 2A has a band medium L, which is typically around 50 MH2. Because this signal has a very wide band,
A priori knowledge of the signal format is usually not easily detected. This is because the total energy contained in this signal is spread over a wide frequency range, so that the signal itself resembles background noise. This signal is typically formed by rapid frequency changes in the transmitted signal, or alternatively by rapid phase changes in the transmitted signal. Detection of such broadband extended spectrum signals is facilitated by the use of the signal processing means 33 of FIG. 1, commonly known as a "matched filter." The matched filter, in some cases, includes a delay line having taps associated with known phase change periods in the extended spectrum code. The output of the signal processing means 33 in response to the desired signal of FIG. 2A is shown in FIG. 3A. Signal processing means 33 time compresses the extended spectrum signal of FIG. 2A to produce output pulses of relatively short duration, typically having a pulse length that is the reciprocal of the signal band length L. Figure 2B shows a narrow band signal with high peak energy.

This is typically a narrow band castle F with a relatively narrow band middle M.
M or CW signal. Such a signal is processed by the signal processing means 33.
, the resulting output is a noise-like signal produced by the decoding action of the signal processing means 33. The narrowband castle signal in FIG. 2B is the signal processing means 33.
Since the signal code for which it is designed is uncorrelated, the output it produces is just noise. Figure 2C shows the broadband desired signal in Figure 2A and Figure 2B.
shows the spectral response of a composite signal containing a narrow band signal of .

Since the narrowband signal with a relatively high peak value in FIG. The resulting output signal shown in FIG. 3C is primarily a narrowband signal and has the same noise-like characteristics as the output shown in FIG. Referring to FIG. 1, switches 14a, 14b, 36
It is clear that with a and 36b in the open position, adaptive filter 10 operates like a conventional IF receiver stage.

The signal supplied to the input terminal 12 is sent to the mixer 18
After frequency conversion, the signal is applied to the synthesizer 22. The output of this synthesizer 22 is given to a signal processing device 33 by an intensifier 32. All signals applied to input boat 12 are subject to changes in IF frequency, e.g.
The signal is applied to the signal processing means 33 in the same manner except for the change from mMHz to 3MHZ. Switches 14a and 36
When a is closed, the adaptive filter 101 includes a single adaptive loop. The presence of the adaptive loop has little effect on the output signal only when the desired signal of FIG. 2A is applied to the input 12 of the adaptive filter. The V-fed signal is applied to a synthesizer 22 by a mixer 18 following frequency conversion.
Delay means 16a provides a delayed reproduction of the output signal to mixer 26a and via limiter 28a to mixer 30a. In mixer 30a, the delayed reproduction signal is mixed with an output signal representing the undelayed combined signal. Since the delayed reproduction signal has undergone a delay of 7, which is the reciprocal of the supplied signal, there is no correlation between the signals supplied to mixer 30a, and the resulting output control signal is This signal is substantially removed by the integrating circuit 34a. Therefore, the control signal supplied to mixer 26a is very weak, and mixer 26a does not supply substantially any output correction signal to synthesizer 22. When the signal applied to input 12 is a composite signal such as that shown in FIG. The bloop acts to suppress narrowband signals in the output signal.

In this case, the composite signal is combined with the synthesizer 22 and the delay means 16.
V is supplied to a. The output of delay means 16a is a delayed reproduction of the composite signal and is supplied to mixer 26a and via limiter 28a to mixer 30a. or,
Mixer 30a is also provided with a sample of the output signal from synthesizer 22, which initially consists of the composite signal that was originally synthesized. In the mixer 30a, there is an interrelationship between the initially supplied narrowband Chiyabu signal of the composite signal and the narrowband Chiyabu signal of the delayed reproduction signal, which is transmitted from the mixer 30a to the local oscillator 20. produces an output signal of the same frequency at the frequency of Assuming two input signals ACOSW,t and BCOSW2t for purposes of explanation, the mixer receives one input signal ACOSW,t and the other input signal BCOSW2t and applies ABCOS to these signals.
W, tCOSW2t=1'2AB{COS(W, -W2
)t+C〇S(W, 10W2)t},
Since it has the general characteristic of generating an output of ABCOS (W, - W2)t, the output signal of mixer 30a is a combination of the composite output signal supplied from synthesizer 22 and IJ
It represents the product of the limited delay reproduction signal supplied from Mitsuta 28a. The dominant part of this product signal is the interference signal component, and by integrating the two signals via the mixer 30a, the intensity of the interference signal increases. Therefore, the output of the mixer 30a mainly represents the interference signal component in the composite output signal in which the interference signal components in the limited delay reproduction signal are integrated. This output represents the phase and amplitude of the interference signal component of the output signal with respect to the phase and amplitude of the interference signal component of the limited delayed reproduction signal provided to mixer 30a.

The output of mixer 30a is integrated by integrator 34a to form a control signal. Integrator 34a is typically a narrow band filter, the width of which is determined by the desired response time of the adaptive filter. The coverage of the integrator 34a does not limit the coverage of the interference signal to be suppressed, but only determines the response time of the adaptive filter 10. The output of integrator 34a is the control signal generated by limiter 28a, mixer 30a, and integrator 34a in response to the delayed reproduction of the composite signal and the output of synthesizer 22. This control signal and delayed reproduction signal are the mixer 26
It is synthesized in a. The control signal provided by integrator 34a modulates the delayed reproduction of the composite signal in mixer 26a to form a correction signal. Since this control signal represents the phase and amplitude of the narrowband signal component of the output signal with respect to the narrowband component of the delayed reproduction signal,
The resulting correction signal is suitable for canceling the output interference signal in the synthesis device 22. mixer 30
The phase between the output signal supplied to a and the delayed reproduction signal needs to be adjusted in order to obtain a correction phase reference for the correction signal for canceling the interfering signal in the synthesizer 22. It will be clear to those skilled in the art. The mixer 30a combines a delayed reproduction signal of the input signal with the intensifier 3.
It is clear that the output control signal of mixer 30a is proportional to the square of the narrowband signal applied to input port 12, since it produces an output signal that is the product of the sampled output of Dew.

In order to create a system with more linear control signal characteristics and therefore a larger dynamic range, limiter 28a is provided to make the control signal output of mixer 30a substantially linear over a wide dynamic range. Therefore, as the power level of the interfering signal increases,
The sampled output from the multiplier 32 increases linearly while the output of the limiter 28a stabilizes at its maximum level, thereby causing the control signal output to vary linearly with the amplitude of the interfering signal to the mixer 30a. emanate from. Adaptive filter 10 is also provided with a second adaptive loop that is connected by closing switches 14b and 36b. It will be clear from FIG. 1 that this second adaptive loop is similar in form and operation to the first adaptive loop described above. When both of these adaptive loops are connected by closing all the switches shown, a single interfering signal will be canceled by the operation of one or both of the adaptive loops of the circuit. Which particular adaptive loop is activated generally depends on small variations in the circuit, such as the gain of each loop, the time constant controlled by the integrator circuit 34, and the delayed reproduction provided to the mixer 30. It depends on the phase of the signal and output. When two narrowband interfering signals are present, both adaptive loops are activated and both of the signals cancel. When no interfering signal is present, there is no correction signal at mixer 30 and the control signal output from mixer 30 consists of a broadband nozzle, which is rejected by integrator circuit 34 so that mixer 2
Little or no power is coupled to the control circuitry to 6. In this case the adaptive loop is effectively cut off. Figure 2D shows that the composite signal of Figure 2C is input to port 1.
2, the output signal of the multiplier 32 is given to the signal processing means 33.

It will be appreciated that the adaptive filter 10 creates a notch in the spectrum of the input signal at the frequency of the narrowband signal, thereby removing a portion of the desired wideband signal and the narrowband signal. Probably. The desired wideband signal also has a notch in frequency separated from the frequency of the narrowband signal by the reciprocal of the delay time of delay line 16a. Since the information provided in the desired broadband signal is spread over the entire frequency band L, these notches in the spectrum of the signal supplied to the signal processing means 33 do not significantly interfere with the reception of the desired information. Since the filter notch provided by the adaptive filter 1 is set based on the narrow band signal, the filter notch changes depending on the fluctuation of the narrow band signal, and the narrow band signal exists. It will be understood that when it disappears, it completely disappears. Since the desired broadband signal is supplied directly to the signal processing means 33 and also by means of an adaptive loop comprising the delay means 16a when the adaptation loop is activated due to the presence of an interfering signal, At the input of the signal processing means 33 are applied two broadband signals which are separated in time by a delay 7 and are therefore illustrated by the two pulses of FIG. 3D separated in time by a delay 1. The signal processing means 33 has two pulse-shaped outputs so that

If the signal applied to input 12 has two narrowband scattering signals and both application loops of adaptive filter 10 are connected, each application loop individually has two narrowband scattering signals. Try to cancel one of the. In this case, the spectrum of the output of the multiplier 32 has one or more notches associated with each of the narrowband signals. From the signal processing means 33 there is also a signal output in the form of pulses associated with each of the two delayed signals and the undelayed input signal, each connected to the summing circuit 22 by an adaptive loop. FIG. 4 is a more detailed block diagram of a current embodiment of the invention.

The embodiment of FIG. 4 shows a complete signal reception and processing system 39 incorporating an adaptive filter according to the invention. Processing system 39 includes a receive antenna 40, a low noise intensifier 41, and a strip filter 42 for processing the received signal at the carrier frequency. Also shown is a mixer 43 and local oscillator 44 for converting the received signal to a convenient IF frequency. In the receiving system 39, the illustrated 11F frequency is 135-29M.
It is HZ. It will be apparent to those skilled in the art that this may be either the first or second IF stage and may include other components not shown. To facilitate the explanation of the receiving system 39, the frequencies and ranges of signals present in various parts of the system are indicated by numbers enclosed in ellipses. All frequencies shown in FIG. 4 are in MHZ. In the receiver 39, the desired signal is assumed to have a bandwidth of 50 MH2, and therefore the received signal after the 11F conversion in the mixer 43 is shown to have a frequency of 139 MHZ to 29 MHZ. Following the conversion in mixer 43, a standard IF band filter 45 and an IF multiplier 46 are shown which provide the received signal to an input terminal 47 of the adaptive filter section of signal receiver 39. The IF signal from terminal 47 is passed through signal splitter 48 to signal splitter 50.
and is supplied to the limiter 54. The signal splitter has five outputs, three of which are delay means 52a,
52b and 52c. The other output of signal splitter 50 is provided to mixer 18. The output of the signal divider 48, which is supplied to the limiter 54, is then supplied to the signal separator 62 by means of an intensifier 56, a bandpass filter 58 and delay matching means 60.

Signal separator 62 has three outputs which are fed to time delay means 64a, 64b and 64c.
As shown in FIG. 4, the delay means 64a is connected to the delay means 52.
It has a delay of 20 microseconds, which is equal to the delay of a.
Similarly, delay means 64b and 52b have equal delays of 40 microseconds, and delay means 52c and 64c have equal delays of 60 microseconds. Delay matching means 60 are provided to equalize the delay of the signals reaching the mixer 30a by correlating the signals by two separate paths. The first abbreviation is the path taken by the signal to be used for comparison, i.e. the limiter 5
4. This path is based on the power divider 62 and delay means 64a. The second abbreviation is an abbreviation taken depending on the feedback signal, which includes the signal divider 50, the time delay means 52a, and the mixer 2.
6a, an intensifier 84a, an adder circuit 22, a divider 68, a phase shifter circuit 70, a power divider 72, and other intervening components. The receiving device 39 is provided with a combining circuit 22 for combining the supplied signals to form an output signal.

One of the signals supplied to this synthesis circuit 22 is supplied to an adaptive filter via a terminal 47, a signal divider 48, and a signal divider 50, converted by a mixer 18, and amplified by a multiplier 83. Consists of signals. Synthesizer 2
The other three inputs to 2 are provided by the three illustrated adaptive lobes having components numbered a, b, and c. The output of the adder circuit 22 is sent to the divider circuit 68 by the bandpass filter 66 and the multiplier 32.
supplied to One output of the signal divider 68 is supplied to the signal processing circuit 33 to form a desired output signal. The other output of the signal dividing means 68 is used as feedback for the three adaptive loops of the adaptive filter of the receiving circuit 39 and is supplied to the power divider 72 via the phase shift circuit 7. The output signal is mixer 18
The mixer 18 uses the output of the local oscillator 20 provided by the power divider 21 to perform the conversion. The feedback signal provided to power divider 72 has the same intermediate frequency and is then applied to mixers 30a, 3.
0b and 30c. Each of these mixers is
There is one for each adaptive loop in the receiving system. Mixers 30a, 30b and 30c are also supplied with delayed reproductions of the received signals which are applied to the outputs of time delay means 64a, 64b and 64c.

It is clear from the accompanying drawing that in the receiving circuit 39 three identical application loops are provided, but for the sake of simplicity only one of them will be described in detail. The output of mixer 30a is provided to baseband filter 78a by bandpass filter 74a and multiplier 76a. This basic band filter 78a is a very narrow band filter and will be further explained in FIG. As shown in FIG. 4, baseband filter 78a requires the use of a signal from local oscillator 20 to operate properly. The output of elementary band filter 78a is a control signal provided to mixer 26a by band filter 80a and multiplier 82a. Also coupled to the mixer 26a is a delayed reproduction signal of the received signal applied to the output of the delay means 52a. The combination of these signals in mixer 26a produces an output correction signal that is at the same frequency as the output signal of mixer 18 and is
is supplied to the synthesizing means 22 according to the following. FIG. 4 shows the phase shift circuit 70 in detail.

The phase shifting circuit 70 employs a mixer 86 which is powered by a local oscillator 88 via a power divider 90 to convert the feedback signal from an IF frequency of 68 MHZ to an IF frequency of 43 MHZ. This conversion is required to facilitate phase shifting of relatively wideband feedback signals. Following filtering in bandpass filter 92, the 43 MHZ signal is conveniently phase shifted by phase shifter 94 and converted back to a 68 MHZ signal in mixer 96. Filter and increase filter 98
and multiplier 100 such that the center frequency is 6
It emits a fully phase shifted signal of 9MH2. This phase shifting circuit is used to finely adjust the phase of the feedback signal supplied to mixer 30a to equalize the phase of the sample signal supplied to mixer 30a via limiter 54 and signal divider 62. When tuning the receiving system 39, the total error in delay introduced by the separate signal paths is:
While the fine adjustment of the phase is achieved by the phase shift circuit 7, the adjustment process is performed by the delay matching means 60. Figure 5 shows the receiving circuit 3.
The details of the basic band filter 78 used in all adaptive loops 9 are shown in the block diagram. The purpose of this basic band filter 78 is to provide very narrow band wave action with a Q of approximately 50,000. This filtering action is desirable as an integral action of the adaptive loop. The general operation of the basic band filter 78 is to convert the 200 MH2 signal output from the mixer 30 into a basic band video signal, filter the basic band video signal, and convert the signal to a 200 MHZ IF. It is.
In order to obtain adequate output from the elementary band filter, it is necessary to maintain in-phase and quadrature signal components.
FIG. 5 shows a basic filter 78 having three terminals. Terminal 102 is an input terminal for the signal to be filtered, and terminal 104
is the output terminal of the signal. A terminal 112 is also provided to which a 20+ MHZ local oscillator signal is supplied.

By using signal divider 114 and phase shifter 116, the in-phase components of the local oscillator signal are transferred to power divider 118.
, and subsequently to mixers 108 and 126, and the quadrature component of the local oscillator signal is applied to power divider 120.
and then to mixers 110 and 128. The intermediate frequency signal to be filtered is provided from terminal 102 to signal splitter 106 and then to mixers 108 and 110. The output of mixer 108 is input terminal 102
is an elementary band video signal representing the in-phase components of the signal fed to the base station. The output of mixer 1 10 is terminal 102
is a baseband video signal representing the quadrature phase shifted component of the signal applied to the baseband video signal. The in-phase and quadrature-shifted fundamental signals are filtered by low pass filters 122 and 124 and provided to mixers 126 and 128. Low-pass filter 12
2 and 124 are selected to have passbands proportional to the desired response time of the adaptive loop. The lower the passband of the filter, the slower the response of the application loop. The outputs of low pass filters 122 and 124 are video signals that are used to directly control the phase and amplitude of a delayed reproduction of the received signal, as described below. However, the outputs of the low-pass filters 122 and 124 are converted back to 2mMH2 IF signals, and the mixer 26 converts this 20MHZ I
By mixing the F signal with the delayed reproduction signal,
It has proven more advantageous to control the amplitude and phase of the delayed reproduction signal of the received signal. This IF signal is reconstituted using mixers 126 and 128 and summing circuit 130 to provide a 200 MH2 IF signal at the output 104 of elementary band filter 78 and finally to mixer 26. The operation of the receiving circuit 39 is as follows.
It will be apparent to those skilled in the art that the operation of the adaptive filter 10 shown in the figures is very similar. In the receiving circuit 39, the received signal at the terminal 47 is converted using the local oscillator 20 and then sent to the mixer 1.
8 directly to the adder circuit 22. Further, the adder circuit 22 is also supplied with signals after frequency conversion by the mixers 26a, 26b and 26c via delay lines 52a, 52b and 52c. The frequency conversion in mixers 26a, 26b and 26c includes adjusting the amplitude and phase of the output of delay line 52 based on the state of the three application loops. The output of the combining (summing) means 22 is fed to a signal processing means 33 and also coupled to mixers 30a, 30b and 30c for interrelation with a delayed reproduction of the received signal provided by a delay line 64. be attached. Adaptive filter included in receiving circuit 39 and adaptive filter 1
The basic difference between the two is that only one limiter 54 is provided and separate delays are provided for the signal fed to mixer 26 and the signal fed to mixer 30. It will be understood that the only thing that can be said is that it is given. This configuration is currently advantageous because the limiter 54
must be very linear in phase and is therefore quite expensive. By using two sets of delay means 52 and 64, it is possible to use only one limiter 54.

Similar to the case of the adaptive filter 10 shown in FIG. 1, the delayed reproduction of the received signal is mixed with the output signal of the combining means 22 in mixer 3. When a narrowband signal exists in the desired signal band, there is a correlation between the output signal and the delayed signal, resulting in an IF control signal with a constant frequency of 20 MHZ,
The signal is used in mixer 26a to provide phase and amplitude control of a delayed reproduction of the received signal to generate a correction signal that is used to cancel the narrowband scattering signal. Illustrated in FIG. 6 is a simplified block diagram of another embodiment of the invention.

The embodiment of FIG. 6 illustrates a technique for implementing the invention without using IF conversion. Shown in FIG. 6 is an adaptive filter 131 that can operate at either IF or carrier frequency. In this adaptive filter 131, the signal initially supplied to V is not frequency-converted, and the signal directly connected to the combining means 22 from the input 12 is also supplied to the delay means 16 and then supplied. Forms a delayed reproduction of the V-fed signal. This delayed reproduction signal is also supplied to mixers 136 and 138 and to mid-shake control 132. This delayed reproduction signal is supplied to the synthesis means 22 by means of an oscillation control device 132 and a phase control device 134. Proper adjustment of the amplitude and phase control devices will allow the amplitude and phase of the delayed reproduction signal to be adjusted to cancel the narrowband signal at the output of the synthesizer 22. The matter is clear. Control signals are supplied to the vibration and phase control devices 132 and 134 to adjust the vibration and phase. In the mixer 136, the delayed reproduction signal provided by the delay means 16 is mixed with the output of the synthesizer 22 to produce an output signal that is in phase with respect to the delayed reproduction signal provided by the delay means 16. An elementary band video signal representing component 1 is formed. The output of the synthesizer 22 is a 900 phase shifter 14
0 to the mixer 138. In mixer 138, a baseband video signal is generated representing an output signal component Q in quadrature with respect to the delayed reproduction signal provided by delay means 16. The in-phase and quadrature video signals produced by mixers 136 and 138 represent error signals due to the presence of narrowband components in the signal provided to input 12. Circuits 142 and 144, either digital or analog, are provided for adjusting and converting the in-phase and quadrature error signals into signals representative of the amplitude and phase of the output signal with respect to the delayed reproduction signal. . In the embodiment of adaptive filter 10 shown in FIG. 1, the control signal is generated by mixer 30a and integrator 34a, although generation of this control signal can be accomplished by a variety of techniques.

For example, in the adapted filter 31 embodiment of FIG. 6, the control signal is generated by the following means. The output signal is assumed to be 0(t), and the delayed reproduction signal is assumed to be C for the sake of explanation.
If OSW3t, 0(t)=ICOSW3t+QS
Since it can be expressed as 1nW3t, the amplitude component of the control signal is determined by taking the square root of the sum of the squares of the in-phase signal component 1 and the quadrature component Q2.

Moreover, the phase component number is determined by the ratio of the in-phase component 1 to the quadrature phase component Q and the polarity of each signal, i.e., 2=n-IQ/1. Therefore, the output signal ○(t) is determined by the polar coordinate format as ○(t)=No20Q2COS{W3t
+J}.

The control signals representing the amplitude and phase are then provided to the amplitude and phase controllers 132 and 134 to provide control of the delayed reproduction signal and thereby the correction to be provided to the synthesizer 22. Generates a signal for use. Apart from the arrangement shown in FIG. 6, controlling the amplitude and phase of the delayed reproduction signal forms a quadrature component of the delayed reproduction signal and using in-phase and quadrature control signals. Synthetic fix 2
This may be accomplished by directly controlling the amount of each of the delayed reproduction signal components that are combined into the second signal.

Although preferred embodiments of the invention have been described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the invention and, therefore, are within the spirit and scope of the invention. All changes and modifications shall be covered.

[Brief explanation of drawings]

1 is a simplified block diagram of an adaptive filter constructed in accordance with the present invention; FIG. 2 is a diagram of the frequency spectrum of the signal generated in the embodiment of FIG. 1;
3 is a diagram showing the time response of the first signal processing means to the signal shown in FIG. 2, FIG. 4 is a detailed block diagram of another embodiment of the present invention, and FIG. FIG. 6 is a detailed diagram of the basic band filter used in the embodiment of FIG. 6, which shows yet another embodiment of the present invention. 10...Adaptive filter, 12...Input, 16a
, 16b... Delay means, 18, 26a, 26b
, 30a, 30b... mixer, 20... local oscillator, 22... adder (synthesizer), 28a, 28
b...Limiter, 33...Signal processing means, 3
9.…”signal reception and processing system, 52a, 52b,
52c... Delay means, 54... Limiter, 64a, 64b, 64c... Delay means. FIG. lFIG. 20 FIG. 5 FIG. 6 FIG. 4

Claims (1)

[Claims] 1. In an adaptive filter that suppresses a narrowband signal in a composite signal containing a desired wideband signal,
signal synthesis means for synthesizing the composite signal and the correction signal to form an output signal in response to the composite signal and the correction signal; means for supplying the composite signal to the synthesis means; means for generating and providing a delayed reproduction of said composite signal in response to a signal; mixer means for generating a control signal in response to said delayed reproduction signal and said output signal; mixer means for controlling the amplitude and phase of the delayed reproduction signal in response to both the reproduced signal and the control signal, thereby generating a correction signal; and supplying the correction signal to the synthesis means. and a stage for suppressing the narrowband interfering signal in the output signal. 2. In an adaptive filter that suppresses a narrowband signal in a composite signal containing a desired wideband signal,
signal synthesis means for synthesizing the composite signal and the correction signal to form an output signal in response to the composite signal and the correction signal; means for supplying the composite signal to the synthesis means; means for generating and providing a delayed reproduction of the composite signal in response to a signal; a phase shifter for receiving the output signal and generating a 90° phase-shifted output signal; a first mixer means responsive to a reproduction signal and said output signal for generating and providing a first signal representing output signal components in phase with respect to said delayed reproduction signal; said delayed reproduction signal and said 90; °
second mixer means for generating and providing a second signal representing output signal components in quadrature with respect to the delayed reproduction signal in response to the phase-shifted output signal; first computing means for generating and providing an amplitude control signal in response to the first signal and the second signal representing the square root of the sum of the squares of the in-phase and quadrature signal components; second computing means responsive to the amplitude control signal for generating and supplying a phase control signal determined by the ratio of the in-phase component to the quadrature phase component and the polarity of each signal; amplitude control means for controlling the amplitude of the delayed reproduction signal; phase control means for controlling the phase of the delayed reproduction signal in response to the phase control signal; and means for supplying a correction signal generated by the control by the phase control means to the synthesis means to suppress the narrowband scattering signal in the output signal. Features an adaptive filter. 3. In an adaptive filter that suppresses a narrowband signal in a composite signal containing a desired wideband signal,
a signal synthesizing means for synthesizing the composite signal and the composite signal to form an output signal in response to the composite signal and the correction signal; means for supplying the composite signal to the synthesizing means; means for generating and providing a delayed reproduction of said composite signal in response to a signal; and a first phase shifter for generating a 90° phase shifted output signal in response to said output signal; a second generator for generating a 90° phase-shifted delayed reproduction signal in response to the delayed reproduction signal;
a first mixer responsive to the delayed reproduction signal and the output signal to generate and provide a first control signal representing output signal components that are in phase with respect to the delayed reproduction signal; means, second mixer means responsive to said delayed reproduction signal and said 90° phase shifted output signal for generating and providing a second control signal representative of output signal components in quadrature with respect to said delayed reproduction signal; , a first control means for controlling the amplitude of the delayed reproduction signal to generate a first correction signal in response to the first control signal; , a second control means for controlling the amplitude of the 90° phase-shifted delayed reproduction signal to generate a second correction signal; and a synthesis means for combining the first and second correction signals. and means for suppressing the narrowband interfering signal in the output signal.